Nowadays mobile communication networks are widely used. These communication networks comprise a plurality of network cells each having at least one base station used to receive and transmit signals from user equipment, e.g. mobile phones or PDAs. A plurality of different environments or systems is known, e.g. GERAN, UTRAN, LTE, E-UTRAN, WCDMA, or WLAN. For ensuring a good performance and in particular an effective data transmission it has to be ensured that all data, data signals, or data packets are received at the intended recipient and at possible relay stations, like base stations of the mobile communication network.
One problem limiting the performance of the data transmission known in the prior art is inter cell and intra cell interference. In order to reduce the inter cell interference some form of cooperative antenna (COOPA) systems are proposed. From theory significant performance gains with respect to capacity and coverage are known for full cooperating cellular radio systems compared to conventional ones. Due to these large gains, which cannot be achieved with other technologies, as it is known from theory that COOPA systems provide an upper bound for interference limited cellular radio systems. At the same time it is clear that full cooperation is not practical due to required channel state information (CSI) to a huge number of base stations (BS) and accordingly large feedback overhead, especially in case of FDD systems. A further topic is the large amount of data on the backbone network, which might generate a lot of costs in terms of CAPEX and OPEX.
In particular, COOPA based on intra eNodeB (eNB) cooperation between adjacent sectors of the site is promising as the most basic cooperation scheme, as it can be implemented without any backbone network involved. Similar are distributed antenna systems (DAS), where the antenna elements (AE) of each sector are spatially distributed. The Tx stations—typically remote radio heads (RRH)—are connected with the baseband unit at the eNB site over fibers, but without inclusion of the backbone network. While intra eNB cooperation can be implemented more easily, larger performance gains require additional cooperation over cells from different sites.
However, COOPA systems require accurate channel estimation, which has to be fed back to the eNBs, where it will be used for precoding in the cooperation area (CA). This channel estimation may be a major challenge, especially due to the inter cell interference from a large number of cells and sites in mobile communication systems. Optimum common references signal (CRS) design may be of utmost importance as a bad design may fundamentally limit the achievable performance for any cooperation scheme in the future.
Thus, there may be a need for a communication network element, a method for transmitting reference signals, a program element, and a computer readable medium providing an improved performance for a multi channel estimation, in particular in a cooperative antenna system.